Physocarpus plant named ‘Donna May’

ABSTRACT

‘Donna May’ is a new and distinct cultivar of  Physocarpus opulifolius  having an upright, mounded, dense plant habit; compact overall plant size; strong branching characteristics; small foliage size; short internode length; purple foliage color throughout the growing season; corymbs of small flowers with pink petals; and ability to root and grow vigorously from softwood and semi-hardwood cuttings.

Latin name of the plant claimed: Physocarpus opulifolius.

Variety denomination: ‘Donna May’.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar ofPhysocarpus opulifolius and will be referred to hereafter by itscultivar name, ‘Donna May’. Physocarpus opulifolius is a deciduous shrubgrown for landscape use. The primary objective of the Physocarpusopulifolius breeding program I initiated in St. Paul, Minn. was todevelop a new Physocarpus opulifolius cultivar that possessed the purplefoliage color of Physocarpus opulifolius ‘Monlo’ (disclosed in U.S.Plant Pat. No. 11,211) and the compact, well-branched growth habit andsmall foliage of Physocarpus opulifolius var. nanus (not patented).

‘Donna May’ originated by crossing an unnamed Physocarpus opulifoliusseedling (code designation of this seeding is 2001-1) as the femaleparent and an unknown plant of Physocarpus opulifolius var. nanus as themale parent. 2001-1 originated from a cross I made between Physocarpusopulifolius ‘Monlo’ (disclosed in U.S. Plant Pat. No. 11,211) as thefemale parent and an unknown plant of Physocarpus opulifolius var. nanusas the male parent. 2001-1 has purple foliage and a growth habit andfoliage size intermediate to its parents. The pollination that led tothe population of progeny that ‘Donna May’ was identified withinoccurred in June 2004. The seeds of this population germinated duringthe winter of 2004/2005 indoors under florescent lights. Seedlings weretransplanted to an outdoor garden bed in St. Paul, Minn. in spring of2005 and ‘Donna May’ was selected as a single plant from the populationof progeny during the summer of 2005. ‘Donna May’ was first asexuallypropagated using semi-hardwood cuttings in the fall of 2005. I havefound that the characteristics of ‘Donna May’ are stable and true totype over successive generations of vegetative propagation.

‘Donna May’ was unique from all other Physocarpus seedlings because ofits dark purple foliage color, very compact, well-branched plant habit,and small foliage. These traits led to it being chosen as an advancedselection in the summer of 2005 and asexually propagated for the firsttime in the fall of 2005. When ‘Donna May’ first flowered in 2006 it wasdiscovered that ‘Donna May’ also possesses attractive flowers with pinkpetals that contrast nicely with the foliage.

SUMMARY OF THE INVENTION

The primary objective of the breeding project was substantiallyachieved, along with other desirable improvements, as evidenced by thefollowing unique combination of characteristics that are outstanding inthe new variety and that distinguish it from its parents, as well asfrom all other varieties of Physocarpus opulifolius of which I am aware:

-   -   1. Upright, mounded, dense plant habit;    -   2. Compact overall plant size;    -   3. Strong branching characteristics;    -   4. Small foliage size;    -   5. Short internode length;    -   6. Purple foliage color throughout the growing season;    -   7. Corymbs of small flowers with pink petals;    -   8. Ability to root and grow vigorously from softwood and        semi-hardwood cuttings.

Asexual reproduction of this new cultivar by rooting softwood andsemi-hardwood cuttings, as performed at St. Paul, Minn. and CottageGrove, Minn., shows that the foregoing and all other characteristics anddistinctions come true to form and are established and transmittedthrough succeeding propagations.

Comparison with Parents

‘Donna May’ has a more compact overall plant size with a denser planthabit than 2001-1. In addition, compared to 2001-1, ‘Donna May’ branchesmuch more freely, has smaller leaves and flowers, and also has shorterinternodes. ‘Donna May’ and 2001-1 share the traits of purple foliagecolor and pink petal color. ‘Donna May’ differs from its male parent,Physocarpus opulifolius var. nanus, in that ‘Donna May’ has purplefoliage color versus green foliage color, darker pink petal color, and aslightly more compact overall plant size. ‘Donna May’ and Physocarpusopulifolius var. nanus are similar in that they both have strongbranching characteristics, a dense plant habit, small foliage, smallflowers, and short internodes.

Comparison of ‘Donna May’ with Similar Cultivars

The Physocarpus opulifolius cultivars with the greatest similarity to‘Donna May’ are ‘Lady in Red’ (disclosed in U.S. Plant Pat. No. 18,660)and ‘Seward’ (disclosed in U.S. Plant Pat. No. 14,821). Both ‘Lady inRed’ and ‘Seward’ grow to be larger at maturity than ‘Donna May’ inoverall plant size and leaf and flower size. Both ‘Lady in Red’ and‘Seward’ also have longer internodes than ‘Donna May’. ‘Lady in Red’ and‘Seward’ are also not as strongly branched and do not have as dense ofplant habit as ‘Donna May’. For instance, four-year-old plants of ‘DonnaMay’ in St. Paul, Minn. in outdoor field plots grew to approximately 1 mtall, while plants of the same age of ‘Seward’ growing in St. Paul,Minn. were approximately 2 m tall.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying colored photographs illustrate the overall appearanceof ‘Donna May’. The photographed plants were four-years-old in the 2009growing season, the growing season when the photographs were taken.These plants were propagated from semi-hardwood cuttings. Photographedplants were growing outdoors within the Twin Cities Metro area in Minn.(Arden Hills, Cottage Grove, and Edina, Minn.). Photographs show thecolors as true as it is reasonably possible to obtain with coloredreproductions of this type. Colors in the photographs may differ fromthe color values cited in the detailed botanical description whichaccurately describe the colors of ‘Donna May’.

FIG. 1 illustrates a plant of ‘Donna May’ growing in an open field infull sun in June 2009.

FIG. 2 illustrates two plants of ‘Donna May’ growing in partial sun in alandscape with other woody plants in September 2009.

FIG. 3 illustrates corymbs of flowers of ‘Donna May’ in mid-June 2009.

FIG. 4 illustrates the strongly branching habit of current season'sgrowth of ‘Donna May’ in August 2009.

FIG. 5 illustrates stems at the base of a plant of ‘Donna May’ withexfoliating bark.

FIG. 6 illustrates representative leaves of 2001-1 (male parent of‘Donna May’; left side of illustration), ‘Donna May’ (middle leaf inillustration), and Physocarpus opulifolius var. nanus (female parent of‘Donna May’; right side of illustration).

DETAILED BOTANICAL DESCRIPTION

The following is a detailed description of ‘Donna May’, the newPhysocarpus opulifolius cultivar, with color descriptions usingterminology in accordance with The Royal Horticultural Society (London)Colour Chart (2001), except where ordinary dictionary significance ofcolor is indicated. The phenotype of the new cultivar may vary withvariations in environmental, climatic, and cultural conditions, as ithas not been tested under all possible environmental conditions.Descriptions are based on observations of four-year-old plantspropagated from stem cuttings and growing in Arden Hills, Cottage Grove,and Edina, Minn.

-   Classification:    -   -   Botanical.—Physocarpus opulifolius ‘Donna May’.        -   Common name of species.—Physocarpus or ninebark.        -   Commercial.—Deciduous shrub.-   Parentage:    -   -   Seed parent.—An unreleased seedling selection designated            2001-1. 2001-1 originated from a cross I made of Physocarpus            opulifolius ‘Monlo’ (disclosed in U.S. Plant Pat. No.            11,211) as the female parent and Physocarpus opulifolius            var. nanus as the male parent. 2001-1 was selected from a            seedling population because it has purple foliage and a            growth habit and foliage size intermediate to its parents.        -   Pollen parent.—Physocarpus opulifolius var. nanus (not            patented).-   General description:    -   -   Plant habit.—Upright, mounded, and compact.        -   Plant size.—1.0-1.2 m in overall height and width.        -   Growth habit.—Vigorous and dense with very strong branching            characteristics.        -   Blooming period.—About 21 days from mid June to early July.        -   Hardiness.—Cold hardy to USDA Zone 3.        -   Root description.—Fibrous and vigorous.        -   Diseases and pest resistance.—No susceptibility or            resistance to diseases or pests known to effect Physocarpus            opulifolius have been observed for ‘Donna May’.        -   Cultural requirements.—‘Donna May’ does well in full to            partial sun and well-drained, moderately fertile soil.-   Growth and propagation:    -   -   Propagation.—Softwood and semi-hardwood stem cuttings have            been effective.        -   Time required for root initiation and initial            development.—It takes about 3 to 4 weeks during the summer            using intermittent mist in the greenhouse without            supplemental lighting for cuttings to generate roots.        -   Time required to obtain a well-rooted cutting.—It takes            about 6 to 7 weeks to produce a well-rooted cutting in a 2            inch container.-   Branch description:    -   -   Branch color.—The color of current season stems is            Greyed-Purple Group 183A. The most mature stems on            four-year-old plants had a mixture of colors on the            exfoliating bark; primarily Greyed-Orange Group 165C, but            there were also areas of Greyed-Orange Group 165A,            Greyed-Orange Group 165B, Greyed-Orange Group 165D and White            Group N155A.        -   Branch size.—Branches produced during the current season of            growth ranged from approximately 15 cm to 60 cm in length            and 1 to 4 mm in width. The oldest branches on four-year            plants were up to 1.5 cm in diameter at the base of the            plant.        -   Branch surface.—Glabrous, smooth, slight sheen.        -   Internode length.—1.5 to 2.0 cm.        -   Branch habit.—Primarily densely foliaged basal branches,            potential for lateral branches any node if pruned.-   Foliage description:    -   -   Leaf size.—Overall leaf length is up to about 4.0 cm            (average 3.75 cm) and 1.0-1.25 cm wide (average 1.2 cm).        -   Leaf division.—Simple.        -   Leaf attachment.—Petiolate.        -   Leaf arrangement.—Alternate.        -   Leaf number.—It varies, but an actively growing branch can            easily produce 30-60 leaves in a growing season.        -   Leaf blade shape.—Ovate in overall leaf blade outline with            three prominent lobes.        -   Leaf blade base.—Rounded to slightly cordate.        -   Leaf blade apex.—Acute.        -   Leaf blade venation.—Primary venation is palmate with three            principal veins. Each principal vein diverges at the            juncture of the leaf blade and petiole and travels through            to the middle of a primary lobe. Secondary venation off of            the three principal veins is pinnate.        -   Leaf blade margin.—The three primarily lobes have secondary            undulations or lobes. The margin on the three primary lobes            is best described then as doubly serrate.        -   Leaf blade surface.—Glabrous on upper and lower surfaces.        -   Leaf blade size.—The leaf blade is approximately 2.5-2.75 cm            long and 1.0-1.25 cm wide.        -   Leaf blade color.—Young emerging leaf blades are            Greyed-Purple Group 183A on the upper and lower surfaces.            Young expanded leaf blades are Greyed-Purple Group 187A on            the upper surface and most of the lower surface except for            veins on the lower surface are Greyed-Green Group 191A.            Mature leaves are Greyed-Purple Group 187A on the upper            surface and Greyed-Green Group 191A throughout the lower            surface.        -   Petiole size.—About 1.0-1.25 cm in length and about 1 mm in            width.        -   Petiole shape.—Sulcate. The petiole is generally round            except for a longitudinal furrow running the length of the            upper surface.        -   Petiole color.—Greyed-Purple Group 183C.        -   Petiole texture.—Glabrous.        -   Stipule number.—There are two stipules at each node with one            on each side of the leaf petiole where it attaches to the            stem.        -   Stipule size.—2-3 mm long and 1.25 mm wide.        -   Stipule shape.—Generally lanceolate.        -   Stipule color.—Greyed-Purple Group 183A.-   Flower description:    -   -   Inflorescence type.—A corymb with 15-25 rotate flowers            arranged in a hemisphere.        -   Inflorescence size.—Typically 1.5-2.0 cm in height and            width.        -   Inflorescence lastingness.—The corymb has open flowers            typically for up to 21 days with each individual flower open            for approximately 3 days.        -   Flower bud shape.—Elliptic.        -   Flower bud size and proportions.—2.5-3.0 mm in length and            2.0 mm in width. The receptacle of the bud accounts for            about two-thirds of the proximal end and the calyx accounts            for about a third of the distal end of the unopened flower            bud.        -   Flower bud color.—The overall color can best be described as            Orange Red Group N34C. The overall base color is green and            it is overlaid with red.        -   Flower size when fully open.—4.0-5.0 mm in diameter and 4.0            mm in depth (not including peduncle).        -   Flower fragrance.—Slight.        -   Petal number.—5.        -   Petal size.—2.5-3.0 mm in length and width.        -   Petal shape.—Elliptic to obovate.        -   Petal color.—Expanding petals are White Group N155B on the            upper surface and White Group N155C on the lower surface.            Fully expanded petals are White Group N155B on both the            upper and lower surfaces.        -   Sepal number.—5.        -   Sepal size.—Length is 3.0 mm and width is 1.5-2.0 mm.        -   Sepal shape.—Deltoid.        -   Sepal color.—Orange Red Group N34C.        -   Peduncle size.—About 1.0 cm in length and 1.0 mm in            diameter.        -   Peduncle color.—Orange Red Group N34C. Green overlaid with            red and relatively consistent in color.        -   Subtending bract size.—There is a subtending bract where            each peduncle meets the central stem of the corymb. The            subtending bract is 2.0-3.0 mm long and 1 mm wide below the            peduncles at the proximal end of the corymb to 1.0-1.25 mm            long and 0.75-1.0 mm wide for the more distal peduncles at            the terminal of the corymb.        -   Subtending bract shape.—Elliptic to obovate.        -   Subtending bract color.—Orange Red Group N34C.-   Gynoecium:    -   -   Pistil number per flower.—Typically there are 4, but            sometimes 3.        -   Stigma shape.—Globular.        -   Stigma size.—0.25 mm.        -   Stigma color.—Yellow Green Group 146D.        -   Style shape.—Linear.        -   Style size.—About 4 mm long and 0.2 mm wide.        -   Style color.—Yellow Group 145D.        -   Ovary shape.—Elliptic.        -   Ovary size.—About 0.3 mm.        -   Ovary color.—Yellow Green Group 145C with portions of Red            Purple Group 73B overlaid.-   Androecium:    -   -   Stamen number per flower.—Approximately 25.        -   Anther shape.—Elliptic to round.        -   Anther size.—0.5 mm.        -   Anther color.—Red Group 53A.        -   Pollen color.—Red Group 53A.        -   Filament shape.—Linear.        -   Filament size.—1.0-3.0 mm long and 0.1-0.2 mm wide.        -   Filament color.—Yellow Group 145D.-   Fruit and seeds:    -   -   Fruit.—There are typically three or four firm-walled            follicles that form per flower. Follicles split along both            sides of the seam, but split more readily along the inner or            adaxial seam. Follicles are elongated and generally ovate in            shape with acuminate tips. They are up to 8.0 mm long and            approximately 2.0 mm wide and range in color from            Greyed-Purple Group 183A to Greyed-Green Group 193A.            Follicle color tends to be green when out of direct sunlight            and increasingly purple the more direct sunlight received.        -   Seeds per follicle.—There are up to 2 seeds per follicle.        -   Seed shape.—Ovate.        -   Seed size.—Up to about 2.0 mm long and 1.25 mm wide.        -   Seed color.—Developing seed is typically Greyed-Yellow Group            161B. Mature seed color is between Greyed-Orange Group 164D            and Greyed-Orange Group 165D.

I claim:
 1. A new and distinct cultivar of Physocarpus opulifolius plantsubstantially as herein shown and described, characterized particularlyby its upright, mounded, dense plant habit; compact overall plant size;strong branching characteristics; small foliage size; short internodelength; purple foliage color throughout the growing season; corymbs ofsmall flowers with pink petals; and ability to root and grow vigorouslyfrom softwood and semi-hardwood cuttings.